Originally posted by COOL 6@Nov 29 2004, 07:38 PM
I was thinking of perhaps going with a very-very lightweight 16" wheel to replace the stock 17"...my reasoning would be if the stock tires suck and we could use some old fasion torque...this could "make it happen".  Do you agree?  If so - what wheel would be tops in style and low mass weight?

Let's put it this way.... do you feel a difference when you drive by yourself vs having 1 passenger with you?

 

Actually it does make a little difference having another person sitting beside you. Just think about it, you're adding 100+ lbs to your car.

But anyway, Cool6, you can buy a lighter 17" rims if you want. The Kosei rims (tireswap.com) is around 13 lbs. That's pretty light!

But heck, if you want the most performance from being lighter, you should strip the car bare. Like Mitsu Evo RS. That car is bare bone.

 

Obviously, the engine output wouldn't change, so you wouldn't be "finding torque." However, directionally speaking the lighter (and smaller diameter) wheel/tire combo would likely also have a lower polar moment of inertia, meaning the wheel experiences a greater angular acceleration for a given amount of torque. Remember, though, that the tire/wheel weight is a tiny part of the mass of the entire vehicle, which must be linearly accelerated. If one's butt dyno could actually detect anything, I'd suspect the presence of the dreaded placebo effect.

The far greater impact would be in the suspension department due to the reduction in unsprung mass, IMHO.

 

Not so garrick, the wheel+tire weight is a large part of the equation. Somewhere someone wrote up an excellent explaination on how this works and hopefully they'll find this thread. I'll probably completely destroy the explaination but anyway, they used some arbitrary numbers to explain it but lets say you have a 100lb wheel+tire combo. So now you have 400lbs of unsprung weight in wheels on your car. Now 100lbs is unreal but the real problem is where is that 100lbs located on the wheel? On the outside of the rim or near the hub? This becomes important in the rotational mass of the wheel which is where another big benefit of smaller/lighter wheels comes into play.

If the majority of the weight is towards the outer most part of the wheel the engine has less of a torque advantage over the wheel. Like a the difference between a plain wrench and a breaker bar. Lets assume that effect of this is 4 times greater than the weight of the wheel. Now it's like adding 400lbs to the car, 4 times, if we have a 100 lbs wheel+tire combo.

 

Since you're thinking that way, why no try 12 or 13's? I didn't know the tires sucked. I doubt that you'll notice the difference in torque. Old fashon torque happened because many old engine had 4 big holes in each side of a steel block for a total of 8. In these holes we had pistons. Some were large enough to eat off of. In many cases these pistons move a great distance in one revolution. That's another reason many onld time torque engine hit maximum hp in the low 5,000 rpm. At best the Mazda 6 has 180 cuin. My old 1970 W-30 Oldsmoble demo has 455 cu in. It was under rated at 370 hp. I would really need to look to confirm the torque.

I really don't think you'll notice any difference. Do you know for sure there is a big weight difference between 16 and 17" wheels

 

Basically in the end, it's not cost effective. You won't feel a difference unless you dropped $$$ for forged rims which will cost $250+ per rim. An air intake will probably give you the same effect at a much lower cost.

 

If you go to lighter 16's, and lower profile tires, you'll change the final drive ratio and give yourself better gearing.

Think of it as a cheap differential gear change. Plus moving to a smaller wheels moves the entire wheel/tire mass in, reducing its overall effect on unsprung weight.

As show in other threads, going from 18x8 +50 rx8 wheels (225/45/18) 48-49 lbs (combined) to 16x8 +50 rx7 wheels (225/50r16) (36-37 lbs), shaved 0.5 seconds off Otaking's 1/4 mile time in his 6i ATX.

Less unsprung weight + smaller diameter tire + better gearing = ultimate pwn!

Roughly about 5x the effect of a cold air intake in overall acceleration.

Did I mention that 16's are cheap as hell? As are the tires! You can pick up a set of FORGED rx7 wheels for close to nothing. (400 for a set of 4 if your frugal and look around)

Remember the stock 16 and 17 inch rims are 23 lbs...so pretty much everything is better .

 

Here's a bunch of articles, threads, links on the subject at hand.

Threads

How much does wheel weight really matter?
http://corner-carvers.com/forums/showthrea...rung+and+weight

Are 18" wheels and tires bling bling or a performance advantage?
http://corner-carvers.com/forums/showthrea...heel+and+weight

How much will 17" wheels slow you down
http://www.sccaforums.com/cgi-bin/ultimatebb.cgi/topic/7/303?

Effect of Lighter Wheels?
http://www.sccaforums.com/cgi-bin/ultimatebb.cgi/topic/7/301?

Rotational Advice
http://forum.miata.net/ubb/ultimatebb.php?...=3;t=002795;p=1

If larger wheels are bad...why do sports cars have them?...
http://forum.miata.net/cgi-bin/ultimatebb....ic;f=3;t=005169

Wheel Weight, Who Cares?
http://forum.miata.net/cgi-bin/ultimatebb....ic;f=3;t=007412

1 Lb of unsprung weight =?? Static weight
http://forum.miata.net/cgi-bin/ultimatebb....f=3;t=006390;p=

0-60 simplified wheel physics and garfield's wheel test
http://www.mini2.com/forum/showthread.php?...3730#post279748

Spreadsheet blows lid off lightweight wheel debate!!!
http://www.mini2.com/forum/showthread.php?s=&threadid=14738

6tech Article
http://www.mazda6tech.com/index.php?option...id=16&Itemid=32

Wheel Weight and Performance
http://forum.mazda6tech.com/viewtopic.php?...der=asc&start=0

Some Wheel Weight Sites
http://www.wheelweights.net
http://www.wheelspecs.com
http://www.miata.net/garage/garagetires.html

Here's a link to Otaking and MrTea's Wild Ride...
http://forum.mazda6tech.com/about1762-0.html

Primary disadvantage of the smaller rims is...

1) All the GBOGH people will laugh at you.
2) You have to be careful to pick a reinforced tire with a good load rating.
3) Your speedo will be off as much as 8-10%.

Do realize that starting a debate on this subject will result in a massive firestorm of flaming and yelling, as large diameter wheels carry a heavy financial and emotional burden for their owners, who will defend them to the last man.

 

Don't give him the wrong encouragement.....

OK, yeah, if you don't mind having two sets of wheels and you want this lightweight set to be for track only use.... Then go right ahead and get smaller wheels and smaller tires. But if this is going to be your everyday set of wheels....
1) Like previously stated, getting smaller tires is going to throw off the speedo and odometer.
2) OR if you're going to try to preserve the OE tire diameter, handling is going to suffer because of the bigger sloppy sidewall.

 

Originally posted by flarearrow@Nov 30 2004, 05:04 PM
2) OR if you're going to try to preserve the OE tire diameter, handling is going to suffer because of the bigger sloppy sidewall.

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A bigger sidewall isn't nec sloppy. If he's upgrading his rims, he'l be upgrading his tires too, and there is a good chance that a higher performance tire will have a stiffer sidewall. If all things remained the same, and he used the same michefailure tires just in 16, yeah it would probably suck, but who the hell would do that?

I believe that smaller, lighter rims with good performance rubber can provide significant improvements to the stock pieces.

The major problem with lightweight rims is they are more susceptable to getting bent or damaged by road hazards

Basically it's going to take a lot of research to get a good wheel tire combo that will give you the effects you are looking for, But it can be done.

 

Originally posted by DaveRulz@Dec 2 2004, 04:15 PM
A bigger sidewall isn't nec sloppy. If he's upgrading his rims, he'l be upgrading his tires too, and there is a good chance that a higher performance tire will have a stiffer sidewall.

My Altima had OE 16's and I wrapped them in 205-55-16 Dunlop SP5000 assymetrics. When I went to 17's with 215-45-17 Falken Ziex 512's, I noticed the difference in steering feel and response right away after taking the first turn out of my driveway.

 

Would have experienced the same thing, but with far better acceleration, had you gone to 215/45/16's. Of course your speedo would have been off another 4%, but it was already off with the 17's, might as well get the performance advantage and the tire/wheel cost savings.

Nice thing about 16's is their pretty inexpensive. I just picked up some 16 rx8 rims for 250 for a set of 4.

 

There's a big thread about this on 6tech; your rims aren't that heavy to start with, but even if you manage to drop 10 pounds on each wheel (40 pounds total), you basically get the effect of dropping 80-100 pounds off the vehicle. However, it'll be hard to drop 10 pounds off each wheel; you'll probably end up dropping 5 or 6 pounds each, for a total of about 20 pounds. Basically, if you lose 40 or 50 pounds somewhere else, it's just as good as lighter rims.

Go on the Atkins diet

Just kidding; as a biochemistry major, I feel obligated to tell you to never resort to the low-carb craze.

 

I have been looking around and YES I think I like the stock wheels...someone has the 18" Stock RX 8 wheels on their car and they look great. I would surmise if one were to put on the 16" wheels you would accelerate the speedo increasing the appearance of "miles" accumulated on your car. The RX 8 wheels being bigger rotating less should give the added benefit of the appearance of "less" accumulated miles overall. I guess what I am saying is the more I look at stock - the better they look. If I was going to make a move...I would ask the dealer to set me up with the RX 8 wheels...but...that must cost a fortune...

 

Stretch went from 16x8 rx7 wheels to 18x8 rx8 wheels and thought he lost a cylinder in his car the performance drop was so big. I like how the entire thread started out about performance, you got about 20+ url's of evidence...and then you decide to just go for the bling.

Next start a thread called "I want less downforce", and then end the thread by buying a giant carbon fiber wing.

And btw rx8 rims are really cheap. Just hit up rx8club.com, or ebay. I've seen people snag sets, with TIRES, for less then 600.

 

Stop - your too funny - I got the idea in the end that I would "do nothing" about swaping the rims as I do like the "look" of the stock wheels...I was thinking in the end barring performance that going with the 16" would run up the speedo and milage by a false 10% (not good) so I was left with upsizing (not good eihter) to the 18" which I would not do...but they do look good (bling) (bling) - Crossbow - Thank you very much for all the threads - you are the resident "genious" here and your efforts as far as disbursing information do not go unnoticed...based on your input as well as others...I will just upgrade to a better set of TIRES (all season) and forgo the rim change...bling...bling...bling...I am an old timer (38) and have no blanking idea what "bling" is...but...from the context - "bling" must be "show and no go"... learning more everyday...I guess...

 

dang...did i hear a bell?

because someone just got schooled.

 

um...please provide also a pick of EVO size WING...Thank You...

 

Primary disadvantage of the smaller rims is...

2) You have to be careful to pick a reinforced tire with a good load rating.

Actually, the opposite is usually true. Going to larger rims, say from 16 to 17, 18, 19, etc, can require looking for a reinforced tire because the smaller air chamber can't hold as much load at the same pressure. The casing is reinforced in order to allow it to hold more air, thus more load.

Going to smaller wheels, like from 17 to 16, assuming same overall diameter of the tire, actually can increase load capacity(larger air chamber), thus negating the need to look for reinforced tires in the vast majority of cases(of course there are exceptions to every rule if anyone is going to post "well, why isn't that true in such and such case?"). The important thing is to make sure your replacement tire load index is equal to or greater than the original equipment tire.

 

Toyoguy,

Aye but I was also pointing out to maintain a smaller profile tire (aka to change your final gear ratio) you'd have to still watch for the load rating...running a 225/45/16 for example...